1. Field of the Invention
The present invention relates to active carbon used for deodorization, and a process for the preparation thereof. More particularly, the present invention relates to a deodorizing active carbon providing an excellent deodorization of a bad smell in a gas phase, especially a smell of tobacco smoke.
2. Description of the Related Art
In general, active carbon provides an excellent deodorizing of a bad smell in a gas phase, even at a low concentration, and is widely used as a deodorant. Nevertheless, active carbon is defective in that the deodorizing capacity thereof with regard to a component stimulant at a low concentration, such as hydrogen sulfide, acetaldehyde or ammonia, is low. As the means for overcoming this defect, there are known a process in which a low-molecular-weight amine is deposited on active carbon to remove an aldehyde (see Japanese Unexamined Patent Publication No. 60-202735), and a process in which an organic silane compound and an essential oil are added in combination and the smell of hydrogen sulfide or ammonia is removed by utilizing volatile components (see Japanese Unexamined Patent Publication No. 63-168171).
Furthermore, there have been proposed a process in which active carbon is subjected to a low-temperature plasma treatment using an amino group-containing compound such as ammonia or an organic amine, a process in which an amino group is introduced into active carbon by a physical means of an irradiation with energy rays such as ultraviolet rays or electron beams (see Japanese Unexamined Patent Publication No. 62-263377), and a process in which active carbon is treated with ozone, hydrogen peroxide or sulfuric acid to introduce an electron donor functional group into the surface of graphite and a metal ion is coordinated with the graphite to form a chelate structure (Japanese Unexamined Patent Publication No. 62-191040).
Nevertheless, the process of supporting (depositing) a compound having a deodorizing capacity on the surface of active carbon is defective in that, since the deposited substance is not tightly fixed to the carrier, the deposited substance drops off during use or the deposited substance is separated during a wet process, and thus the performance thereof is drastically reduced. Furthermore, according to this process, the deposited substance is adhered unevenly to the carrier, and thus the functional group is not effectively utilized.
The above process of chemically bonding a functional group to the surface of active carbon can be theoretically established, but from the industrial viewpoint, the process is very complicated, and in view of the shape, efficiency and safety, the process cannot be practically applied to a carbon fiber or active carbon. Moreover, it is difficult to introduce the deodorizing component in the form of an effective primary amine, and it is difficult to control a formation of an inactive secondary or tertiary amine, which is not effective, and thus the deodorizing performance is poor.